Die casting apparatus

ABSTRACT

The present invention provides improved apparatus for casting dies and the like. Basically, the apparatus comprises a container for holding molten material that is to be cast into an article, such as a die or the like, having a cavity of a desired shape formed therein; a plunger mounted for movement into and out of the container and mounting an embossed master of the desired cavity shape that can be impressed into the molten material; and seal means mounted around the outer periphery of the plunger to provide a fluid-tight seal between the plunger and the interior of the container. The seal means has a coefficient of expansion which is greater than that of the container and plunger and has a melting point which is greater than that of the material to be cast.

United States Patent 11 1 1111 3,815,663

OConnor et al. [4 1 June 11, 1974 [54] DIE CASTING APPARATUS FOREIGN PATENTS OR APPLICATl O NS 1 Inventors: J OC 3020 Curran 45-32334 10/1970 Japan 164/113 Rd., Lou1sv11le, Ky. 40205; Joseph Newman, Loulsvlne, y- Primary Examiner-J. Spencer Overholser [73] Assignee: said OConnor, by said'Newman, Assistant bummer-John Roethel Louisville Ky Attorney, Agent, or F1rmHarry B. ODonnell, [11

[22] Filed: Feb. 18, 1972 [57 CT [21] Appl. No.: 227,383- The present invention provides improved apparatus for casting dies and the like. Basically, the apparatus 1 comprises a container for holding molten material that 2% 164/ 2 2 1 14 62 is to be cast into an article, such as a die or the like, d 321 113 having a cavity of a desired shape formed therein; a l 1 o arc 1 64/31 plunger mounted for movement into and out of the container and mounting an embossed master of the V desired cavity shape that can be impressed into the [56] References C'ted molten material; and seal means mounted around the UNITED STATES PATENTS outer periphery of the plunger to provide a fluid-tight 1,938,257 12/1933 Jones 164/120 seal between the plunger and the interior of the conl.956,907 5/1934 Miller et a1... 164/120 tainer. The seal means has a coefficient of expansion 2,381,625 8/1945 Stewart 164/80 X is greater than that of the container and plunger 2,932,865 4/1960 Bauer 164/113 and has a melting point which is greater than that of 3,254,377 6/1966 Morton 164/312 the material to b cast 3,300,822 1/1967 Thompson.... 164/312 3,613,768 10/1971 Awano et a1 164/120 1 16 Claims, 9 Drawing Figures DIE CASTING APPARATUS BACKGROUND OF THE INVENTION This invention relates to casting apparatus and, more particularly, to apparatus for casting molten material under pressure into an article such as a die or the like having a cavity of a desired shape formed in it.

In the past, various unsuccessful attempts have been made to cast molten material into a die having a cavity of a desired shape therein that was of sufficient quality to be used in molding items made of compounds of elastomers, plastics and the like.

Because of this lack of success in casting, it has heretofore been necessary to form the cavities in such dies by cold working a piece of solid material, as by cutting in the cavity of the desired shape with machines such as lathes, mills, etc. Such machining has been both lengthy and costly and must be followed up by manually rubbing the cavity surfaces to a smooth finish with abrasives. In an effort to overcome this great expense, renewed attempts have been made at casting, wherein the molten material has been held in a container and a plunger has been mounted for movement into and out of the container that mounts an embossed master of the desired cavity shape that can be plunged into the molten material under pressure. Heretofore, however, such attempts at pressurized casting have been fraught with problems of impracticality and safety, because the pressurized molten material would squirt out between the plunger'outer periphery and the container interior.

The present invention provides apparatus which overcomes the aforenoted problems which have heretofore been encountered with pressurized casting and enables successful casting of motlen material into a die having a cavity of a desired shape therein which is of sufficient quality for use in molding items made of compounds of elastomers, plastics and the like and, thus, eliminates the aforenoted previously required expensive machining and abrading operations.

SUMMARY OF THE INVENTION The present invention provides improved apparatus for casting dies and the like.

' Basically, the apparatus provided by the present invention comprises a container for holding molten material that is to be cast into an article, such as a die or the like, having a cavity of a-desired shape formed therein; a plunger mounted for movement into and out of the container and mounting an embossed master of the desired shape that can be impressed into the molten material; and seal means mounted around the outer periphery of the plunger to provide a fluid-tight seal between the plunger and the interior of the container. The seal means has acoefficie'nt of expansion which is greater than that of the container and plunger and has a melting point which is greater than that of the material to be cast.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a perspective view of a form of an article which can be cast by the apparatus of FIG. 1;

FIG. 3 is an enlarged sectional view taken generally along line 33 of FIG. 1;

FIGS. 4, 5 and 6 are fragmentary schematic views illustrating the relationship of the plunger, container, seal means and stripper means of the apparatus of FIG. 1 in three different conditions of the operation of the apparatus shown in FIGS. 1 and 3;

FIG. 7 is a sectional view taken along line 7-7 of FIG. 3;

FIG. 8 is a greatly enlarged schematic view illustrating in detail the construction of the plunger, container and seal means of the apparatus shown in FIGS. 1 and 3-7; and

FIG. 9 is a schematic diagram of presently preferred control means that can be employed with the apparatus of the present invention.

DETAILED DESCRIPTION Referring now to the drawings, and, more particularly, to FIGS. 1 and 3-9 thereof, there is illustrated a presently preferred form of apparatus 10 that is provided in accordance with the present invention. The apparatus 10 is particularly adapted for casting molten material under pressure to form a solid article, such as a die 11' or the like (shown in detail in FIG. 2), which has a cavity 12 of a desired shape formed therein that is of sufficient quality to be used for molding items made of compounds of elastomers, plastics and the like.-

In the past, various unsuccessful attempts have been made to castmolten material into an article, such as the die 11, having a cavity, such as the cavity 12, of a desired shape formed therein that was of sufficient quality to be used for molding items made of compounds of elastomers, plastics and the like. Because of this lack of success in casting, it has heretofore been necessary to form the cavities in such dies by cold working a piece of solid material, as by cutting in the cavity which machines such as lathes, mills, etc. Such machining has been both lengthy and costly and must be followed up by mechanically rubbing the cavitysurfaces to a smooth finish with abrasives. In an effort'to overcome this great expense, renewed attempts have been made at casting. However, up until now, such attempts at pressurized casting have been fraught with problems of impracticality and safety.

The apparatus 10 which is provided in accordance with the present invention overcomes these aforenoted problems that have heretofore been encountered with pressurized casting and, thus, eliminates the aforenoted previously required expensive machining and abrading operations.

As illustrated in FIGS. 1 and 3-9, the presently preferred form of the apparatus 10 of the present invention comprises a container 13 for holding molten material that is to be cast into an article, such as the die 11 or the like, having a cavity, such as the cavity 12, of the desired shape formed therein; a plunger 14 mounted for movement into and out of the container 13 and mounting an embossed master 15 of the desired shape of the cavity 12 that can be impressed into the molten material; and seal means 16 mounted around the outer periphery of the plunger 14 to provide a fluid-tight seal between the plunger 14 and the interior of the container 13. In particular accordance with the present invention, the seal means 16 has a coefficient of expansion which is greater than that of the container 13 and plunger 14 and has a melting point which is greater than that of the material to be cast to form the article 11.

As further shown in FIGS. 1 and 3-9, the apparatus includes a rectangular base member 17 which is adapted to be generally horizontally arranged on a surface such as a table top or the like (not shown). Projecting upwardly from each of the four corners of the base member 17 are four uprights 18 which, in turn, support a rectangular top plate 19 and interconnect it to the base member 17. The top plate 19 is provided with a central opening 20 through which downwardly passes a reciprocably movable piston rod 21 of a fluid motor drive means, such as a so called hydraulic cylinder motor or'the like 22, which has its cylinder 23 fixed to the top plate 19 by suitable fastening means, such as welding or the like. The lower end of the piston rod 21 is connected, as by threads 24, to the top of the plunger 14, which also hasthe master shape removably fastened, as by threads 25, to the radial center of its bottom surface. The container 13 is in the form of a cup which has its lower exterior surrounded by an electri- Cally-powered resistance heater 26 that is, in turn, supported on the base member 17 such that the radial centers of the container 13 and the plunger-carried master shape 15 are axially aligned with one another.

As best shown in FIGS. 1, 3 and 8-9, the heater 26 is connected across a pair of electric power lines L and L in electrical series with a normally-open switch 28 by conductors 29 and 30. The upper end of the piston rod 21 of the fluid motor drive means 22 carries a piston 31 that is contained within the cylinder 23. The interior portion of the cylinder 23 below the piston 31 is fluid connected by a first conduit 32u to a first outlet port 33u of a multiposition control valve 33, whereas the interior portion of the cylinder 23 above the piston 31 is connected by a second conduit 32d, which also includes a pressure gage 32g, to a second outlet port 33d of the valve 33. The valve 33 has its single inlet port 331' connected to a source of pressurized fluid (as shown in block in FIG. 9) by a third conduit 34. Coolant can be supplied to a hollow space 14s provided in the interior of the plunger 14 from a source of pressurized coolant (also shown in block in FIG. 9) that is connected to the plunger interior space 14s in series with a gate valve 14v through a coolant supply conduit 141', and a drain conduit 14d is also provided for discharging the coolant from the plunger hollow space 14s.

With the foregoing arrangement, a solid billet 11s (FIG. 4) of the material that is to be cast into the die 11 (FIGS. 2 and 6) can be placed into the container cup 13 (FIG. 4) and then be changed into its molten state 11m (FIG. 5) through energization of the heater 26 by closure of the switch 28. Then, the plunger 14 and the master shape 15 carried by itcan be moved into and out of the container 13 through operation of the multi-position control valve 33. For example,

movement of the plug cock 330 of the control valve 33 to a first position (shown in solid lines in FIG. 9) fluid connecting the valve inlet port- 331' to the first outlet port 3311 will supply pressurized fluid to the bottom of the piston 31 and cause upward movement of the plunger 14 toward movement out of the container cup 13, whereas movement of the plug cock 33c to a second position (shown in shadow in FIG. 9) fluid connecting the valve inlet port 33i to a second outlet port 3311 (and thus also concurrently disconnecting the first outlet port 33a from the inlet port 33i) will cause pressurized fluid to be supplied to the top of the piston 31 and thus cause the plunger to be moved downwardly toward the container cup 13.

In accordance with a particularly important aspect of the present invention, the seal means 16 is removably mounted around the outer periphery of the plunger 14 to provide a fluid-tight seal between the plunger 14 and the interior of the container cup 13 when the plunger 14 and the master shape 15 carried by it are driven downwardly into'the container-held molten material 11m under pressure by the action of the pressurized fluid on the top of the piston 31 of the drive means 22. Basically, the present invention achieves such a fluidtight seal by making the seal means 16 of a material that has a coefficient of expansion which is greater than that of the container 13 and the plunger 14, and has a melting point which is greater than that of the material 11s that is to be cast into the article or die 11. It has been found to be further advantageous, in accordance with the present invention, to form the outer periphery of the plunger 14 and theinterior of the seal means 16 with complementary tapers, to also form the exterior of the seal means 16 and the interior of the container 13 with complementary tapers, and to make the seal means 16 of a material having inherent lubricity.

In the illustrated form of the present invention (note especially FIG. 8) the container 13 is-in the form of'a cup, the interior of which includes a generally horizontal bottom wall having tapered side walls extending upwardly therefrom, while the plunger 14 has the shape of a truncated cone. The seal means 16 is in the form of a ring, the tapered interior of which surrounds the tapered lower outer periphery of the plunger 14 and the exterior of which is made complementary to the shape of the upper portion of the tapered side walls of interior of container 13.

In using a zinc-based alloy, such as Formaloy Die Metal No. 2 sold by Federated Metals Division of American Smelting and Refining Company of Whiting, Indiana, which has a melting point of about 750F for the material (FIG. 4) that is to be changed into its molten state 11m (FIG. 5) and cast under pressure in the apparatus 10 to form the article 11 (FIGS. 2 and 6), good results have been obtained by employing a container 13 and a plunger 14 which were both made of carbon steel and a seal means ring 16 made of aluminum and by using complementary downward tapers offset from the vertical at an angle 6 of about 3 between the periphery of the plunger 14 and the interior of the seal means ring 16 and offset from the vertical at angle a of about 1 between the exterior of the seal means ring 16 and the upstanding side walls of the interior of the container cup 13 (FIG. 8). And, the embossed master shape 15 used was machined from No. 303 Stainless Steel.

To cast an article, such as the die 11, with the apparatus 10, an operator first moves the plug cock 330 of the control valve 33 to its first position (FIG. 9 solid lines) directing pressurized fluid through the valve inlet 33i, outlet 33a, conduit 32a and against the bottom of the drive means piston 31 causing the plunger 14 to be moved upwardly out of and well above the container cup 13. Then, the removable seal means ring 16 is slipped over the bottom of the plunger 14 and into engagement with the lower outer periphery of the plunger 14.

Next, the previously machined embossed master 15 i of the desired shape of the cavity 12 is affixed to the bottom center of the plunger 14 by threads 25. Then, the billet of the solid material 115 that is to be formed into the die 11 is placed into the container 13 (FIG. 4) and changed into its molten state 11m (FIG. 5) by energization of the heater 26 through closure of the switch 28. During the early part of this melting step, the plunger 14 and the master shape 15 and seal means 16 which are now attached to it are moved close to the top of but not into the container cup 13 by rotating the valve plug cock 33c to its second position (FIG. 9 shadow lines) directing pressurized fluid through the valve inlet 33i, outlet 33d, conduit 32d and against the top of the piston 31. As shown in FIG. 4, this will cause the lower tip of the master shape 15 to be engaged with the top of the billet of solid material 11s and result in preheating of the plunger 14 and the attached master shape 15 and seal means ring 16.

Just before the billet of solid material 11s is changed to its molten state 11m. the plug cock 330 is returned to its first position (FIG. 9 solid lines) raising the plunger 14 and its attached master shape 15 and seal means ring 16 away from the container 13 sufficiently to permit the operator to skim slag from the top of the molten material 11m. As soon as this slag has been skimmed, the operator returns the valve plug cock 330 to its second position (FIG. 9 shadow lines) redirecting the pressurized fluid against the top of the piston 31 and ramming the plunger 14 and its attached master shape 15 and seal means ring 16 into the container cup 13 which now holds themolten material 11m, and causing the master 15 to be impressed into the upper surface of the molten material 11m. At this time, the tapered exterior of the more rapidly thermally expanding seal means ring 16 is rammed into fluid-tight engagement with the upper portion of the complementary tapered interior side walls of the container 13 by the pressurized downward movement of the tapered outer periphery of the lower thermally expanding plunger 14 against the complementary tapered interior of the more rapidly thermally expanding seal means ring 16.

The heater 26' is now immediately de-energized by opening the switch 28 and the now pressurized and shape impressed molten material 11s is allowed to cool until resolidified into the die 11, having the cavity 12 formed therein. This cooling and resolidification is preferably further promoted by opening the coolant valve 14v to supply coolant to the plunger hollow space 14s.

It is then necessary to separate the resolidified and cast die 11 from the container 13, the plunger 14, the master shape 15 and the seal means 16 which, following resolidification of the material forming the die 11, are all stuck together. In accordance with the present invention, the separation of these parts is facilitated by making the seal means ring 16 of a material having inherent lubricity, and is further eased by providing the apparatus with mechanical stripping means.

As illustrated, these stripping means include two sets of diametrically opposed stripper rods 35 and 36 that are suspended from the top plate 19 of the apparatus 10. The first set of stripper rods 35 are horizontally 6 spaced apart from one another such that they will engage the container 13 but will not engage the plunger 14, the seal'means ring 6 nor the resolidified cast die 11 upon upward movement of the stuck together container 13, plunger 14, master shape and seal means ring 16 by movement of the plug cock 33c to its first 5 position (FIG. 9 solid lines). The second set of stripper rods 36 are angularly offset from, and extend downwardly from the top plate 19 a lesser distance than, the first set of stripper rods 35 and are horizontally spaced apart from one and other such that they will engage the 0 top of the seal means ring 16 but will not engage the container 13, the plunger 14 nor the resolidified and cast die 11 upon upward movement of the then stuck together container 13, plunger 14, master shape 15 and seal means ring 16 by rotation of the plug cock 33c to its first position (FIG. 9 solid lines). With this arrangement (as best shown in FIG. 6), the container 13 will be engaged by the first set of stripper rods 35 and stripped free from the bottom and sides of the resolidified and cast die 11, while the top of the seal means ring 16 will be engaged by the second set of stripper rods 36 and stripped free from the upwardly moving plunger 14 and will, in turn, strip the top of the resolidified and cast die 11 free from the bottom of the master shape 15 and the plunger 14. Then, the seal means ring 16 can be knocked free from the top of the stripped resolidified and cast die 11.

In further accordance with the present invention, it has been found that separation of the seal means ring 16 from the container cup 13 and plunger 14 can be still further facilitated by applying a lubricant, such as paste graphite or the like, to the seal means ring 16 prior to its aforenoted engagement around the lower outer periphery of the plunger 14.

With the apparatus 10 constructed and utilized as described above, a single machined embossed master shape, such as the master shape 15, can be used many times to cast-a plurality of articles, such as the die 11, having a cavity of that desired shape, such as the cavity 12, formed therein that is of sufficient quality to be used in molding compounds made of elastomers, plastics and the like. Thus, machining costs can be tremendously reduced.

It should be apparent that while there has been described what is presently considered to be a presently preferred form of the present invention in accordance with the Patent Statutes, changes may be made in the disclosed apparatus without departing from the true spirit and scope of this invention. For example, other equivalent forms of drive means, such as jack screws or the like, might be substituted for the illustrated fluid motor drive means 22. Also, various other materials might be utilized for the material to be cast or for the materials of construction of the container 13, plunger 14, master shape 15 and seal means 16.

What is claimed is:

l. Apparatus for casting dies and the like, comprismg:

a. a container for holding molten material that is to be cast into an article having a cavity of a desired shape formed therein;

b. a plunger mounted for movement into and out of said container and mounting an embossed master of said desired shape that can be impressed into said molten material; and

c. seal means mounted around the outer periphery of said plunger to provide afluid-tight seal between said plunger and the interior of said container,

d. said seal means having a coefficient of expansion which is greater than that of said container and plunger and having a melting point which is greater than that of said material.

2. The invention of claim 1, further including means for heating said container to melt said material.

3. The invention of claim 2, further including means for cooling said plunger. 7

4. The invention of claim 3, further including drive means for driving said plunger into and out of said container.

5. The invention of claim 1, further including means for cooling said plunger.

6. The invention of claim 1, further including drive means for driving said plunger into and out of said container.

7. The invention of claim 1, wherein said seal means is removably mounted on said plunger.

8. The invention of claim 7, wherein said seal means possesses sufficient lubricity to facilitate its ready removal from said container and said plunger after said material has had said desired shape impressed therein and has been allowed to solidify in said container.

9. The invention of claim 1, wherein said seal means possesses sufficient lubricity to facilitate its ready removal from said container after said material has had said desired shape impressed therein and has been allowed to solidify in said container.

10. The invention of claim 1, wherein said container and plunger are made ofsteel, said seal means is made of aluminum, and said material to be cast is an alloy having a melting point of about 750F.

11. The invention of claim 1, wherein said plunger outer periphery and the interior of said seal means are formed with complementary tapers.

12. The invention of claim 11, wherein the exterior of said seal means and said container interior are formed with complmentary tapers.

13. The invention of claim 1, wherein the exterior of said seal means and said container interior are formed with complementary tapers.

14. The invention of claim 1, further including means for stripping said article free from said container after said material has had said desired shape impressed therein and has been allowed to solidify in said container.

15. The invention of claim 14, further including means for stripping said article free from said plunger after said material has had said desired shape impressed therein and has been allowed to solidify.

16. The invention of claim 1, further including means for stripping said article free from said plunger after said material has had said desired shape impressed therein and has been allowed to solidify. 

1. Apparatus for casting dies and the like, comprising: a. a container for holding molten material that is to be cast into an article having a cavity of a desired shape formed therein; b. a plunger mounted for movement into and out of said container and mounting an embossed master of said desired shape that can be impressed into said molten material; and c. seal means mounted around the outer periphery of said plunger to provide a fluid-tight seal between said plunger and the interior of said container, d. said seal means having a coefficient of expansion which is greater than that of said container and plunger and having a melting point which is greater than that of said material.
 2. The invention of claim 1, further including means for heating said container to melt said material.
 3. The invention of claim 2, further including means for cooling said plunger.
 4. The invention of claim 3, further including drive means for driving said plunger into and out of said container.
 5. The invention of claim 1, further including means for cooling said plunger.
 6. The invention of claim 1, further including drive means for driving said plunger into and out of said container.
 7. The invention of claim 1, wherein said seal means is removably mounted on said plunger.
 8. The invention of claim 7, wherein said seal means possesses sufficient lubricity to facilitate its ready removal from said container and said plunger after said material has had said desired shape impressed therein and has been allowed to solidify in said container.
 9. The invention of claim 1, wherein said seal means possesses sufficient lubricity to facilitate its ready removal from said container after said material has had said desired shape impressed therein and has been allowed to solidify in said container.
 10. The invention of claim 1, wherein said container and plunger are made of steel, said seal means is made of aluminum, and said material to be cast is an alloy having a melting point of about 750*F.
 11. The invention of claim 1, wherein said plunger outer periphery and the interior of said seal means are formed with complementary tapers.
 12. The invention of claim 11, wherein the exterior of said seal means and said container interior are formed with complmentary tapers.
 13. The invention of claim 1, wherein the exterior of said seal means and said container inTerior are formed with complementary tapers.
 14. The invention of claim 1, further including means for stripping said article free from said container after said material has had said desired shape impressed therein and has been allowed to solidify in said container.
 15. The invention of claim 14, further including means for stripping said article free from said plunger after said material has had said desired shape impressed therein and has been allowed to solidify.
 16. The invention of claim 1, further including means for stripping said article free from said plunger after said material has had said desired shape impressed therein and has been allowed to solidify. 